The official Xinhua News Agency said a woman surnamed Hu was arrested last month in Wuhan and is suspected of being part of a group of three people and a network of middlemen who provided gender testing across the city of 4.5 million.

Women usually paid around 700 yuan ($110) for the service, it said.

Gender testing, although banned, is rampant and usually takes place in clinics.

China has an alarmingly high gender imbalance. The government says that last year there were 117.78 boys born to every 100 girls. The natural gender ratio at birth is between 103 and 107 boys to every 100 girls.